1. Field
Embodiments of the disclosure relate generally to the field of optical systems for laser transmission and more particularly to embodiments to combine multiple laser sources using a self-referenced interferometer generated hologram of the optical path to the target to remove optical path aberrations and improving the hologram by making the fringe transfer and blazing for high optical efficiency very insensitive to fringe contrast and intensity fluctuations.
2. Background
Combining of multiple laser beams provides for increased power and other desired characteristics. Current approaches for combination of beams require separate beam control or adaptive optics for each laser beam. Such existing solutions combine the beams with a static grating, requiring separate wavefront control on each laser and do not add the benefit of adaptive optics to also compensate for the path to the target. Additionally very precise piston, tip and tilt tolerances are required in the beam control system and optical trains to maintain the beams within the alignment ranges of the control loops. Existing solutions combine the beams with active steering systems for each beam using a static grating requiring separate piston, tip, and tilt control on each sub-aperture and do not add the benefit of adaptive optics to also compensate for the path to the target. Optical systems which maintain the required high tolerances are complex and expensive. Additionally, conventional adaptive optical devices and controls are fragile and require constant tuning therefore becoming impractical for fieldable systems.
To improve adaptive optics, generation of real time holograms as diffraction gratings may be employed. Interference fringes used to create the holograms may employ blazing for improved performance. The conventional fringe blazing approach involves guessing at a fringe intensity threshold and applying the threshold to all pixels in a row across fringes. The pixels are then binarized (above threshold=1, below threshold=0) and binarized fringes are created by assuming one wave between fringes to generate a high optically efficient stepped blazed grating for transfer to an electrically addressed spatial light modulator for real time hologram beam projection or image compensation applications. This approach is very sensitive to the initial threshold intensity guess and is very sensitive to changes in intensity caused by atmospheric turbulence scintillation, and unbalanced signal and reference leg power levels caused by pinhole losses in the reference leg.
It is therefore desirable to provide a laser beam control system which reduces complexity, size, weight, and power, reduces the adaptive optics requirements to reduce cost while improving far field beam quality and improves blazing of hologram fringes for increased performance.